If they continue not in their unbelief (εαν μη επιμενωσ τη απιστια). Third class condition with the same verb used in verse Romans 11:22 of the Gentile. Locative case of απιστια here (same form as the instrumental in verse Romans 11:20).

For God is able (δυνατος γαρ εστιν ο θεος). See this use of δυνατος εστιν in Romans 4:21 rather than δυνατα. This is the χρυξ of the whole matter. God is able.